1. Technical Field
The present disclosure relates to a vacuum mold and device for drilling extraction holes therein.
2. Description of the Related Art
Generally, common plastic molding includes vacuum molding, injection molding, extrusion molding, compression molding, and blow molding. Vacuum molding is widely used in various industries because of its low cost.
In a typical vacuum molding process, a resin sheet is first positioned on a molding surface of a mold body. The resin sheet is then heated to become soft until the resin sheet deforms into a predetermined shape corresponding to a shape of the molding surface and abuts the molding surface. Gas is vented through the extraction holes to form a vacuum between the deformed resin sheet and the mold body, thereby pulling the deformed soft resin sheet to the molding surface. The deformed resin sheet is then cooled to form the predetermined shape. Finally, compressed gas is injected into the extraction holes to push the molded sheet away from the molding surface.
However, if the extraction holes have too large a diameter, the material of the resin sheet flows into the extraction holes and forms micro-protrusions after cooling. If each extraction hole has too small a diameter and too large a depth, venting the gas in the extraction holes is difficult. As a result, it becomes difficult to pull the resin sheet and difficult to generate a force to push the molded sheet away from the molding surface, resulting in a low yield rate.
Therefore, a vacuum mold and a device for drilling extraction holes in the vacuum mold is desired to overcome the above-described shortcoming.